/**
*      author: Y_Yao
*      created: 2024-11-27 12:52:22
**/

#include<bits/stdc++.h>
#define int LL 
using namespace std;
using LL = long long;
const LL LLINF = 1e18;
const int INF = 0x3f3f3f3f;
const int N = 20 + 10;
int a[N][N],dp[N][N];
int xb,yb,x,y;

void solve()
{
    cin >> xb >> yb >> x >> y;
    x += 1,y += 1;
    xb += 1,yb += 1;
    a[x][y] = 1;
    a[x - 2][y - 1] = 1;
    a[x - 1][y - 2] = 1;
    a[x + 1][y - 2] = 1;
    a[x + 2][y - 1] = 1;
    a[x + 2][y + 1] = 1;
    a[x + 1][y + 2] = 1;
    a[x - 1][y + 2] = 1;
    a[x - 2][y + 1] = 1;

    dp[1][1] = 1;
    for(int i = 1;i <= xb;i++)
    {
        for(int j = 1;j <= yb;j++)
        {
            if(i == 1 && j == 1) continue;
            if(!a[i][j])
            {
                dp[i][j] = dp[i-1][j] + dp[i][j-1];
            }
        }
    }

    cout << dp[xb][yb] << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}